The Fontan procedure offers a means of palliating the hemodynamic derangements associated with some complex congenital heart lesions. It does so by utilizing systemic venous pressure to drive blood across the pulmonary capillary bed. The result, in most cases, is a chronically elevated systemic venous pressure. Although several authors have raised concerns about the long term effect of this systemic venous hypertension on the liver, no one has systemically evaluated hepatic function in patients who have undergone the Fontan procedure nor characterized the precise biochemical and physiologic abnormalities in these patients. We propose to determine in a cross sectional study the characteristics of hepatic blood flow (galactose clearance, doppler ultrasonography), and hepatic synthetic function (PT, ammonia, cholesterol, clotting factors) in patients who have undergone the Fontan procedure. In the second phase of this study, we will perform a longitudinal study to describe the changes in PT and galactose elimination over time post Fontan to determine if these tests may be useful in monitoring the development of hepatic dysfunction in these patients.